Test winform integration.

src/NTwain/Native/WIN_MESSAGE.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace NTwain.Native
+{
+  /// <summary>
+  /// The MSG structure in Windows for TWAIN use.
+  /// </summary>
+  [StructLayout(LayoutKind.Sequential)]
+  struct WIN_MESSAGE
+  {
+    public IntPtr hwnd;
+    public uint message;
+    public IntPtr wParam;
+    public IntPtr lParam;
+    uint _time;
+    int _x;
+    int _y;
+    uint lprivate;
+  }
+}

src/NTwain/Native/WinformPumpTest.cs

@@ -0,0 +1,14 @@
+#if WINDOWS || NETFRAMEWORK
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace NTwain.Native
+{
+  internal class WinformPumpTest
+  {
+  }
+}
+#endif

src/NTwain/TwainSession.Callbacks.cs

@@ -92,6 +92,11 @@ namespace NTwain
         case MSG.XFERREADY:
           break;
         case MSG.DEVICEEVENT:
+          // use diff thread to get it
+          //if (DGControl.DeviceEvent.Get(ref _appIdentity, ref _currentDS, out TW_DEVICEEVENT de) == STS.SUCCESS)
+          //{
+
+          //}
           break;
         case MSG.CLOSEDSOK:
           DisableSource();
@@ -101,10 +106,5 @@ namespace NTwain
           break;
       }
     }
-
-    public void HandleWin32Message(uint msg)
-    {
-
-    }
   }
 }

src/NTwain/TwainSession.Windows.cs

@@ -0,0 +1,69 @@
+#if WINDOWS || NETFRAMEWORK
+using NTwain.Data;
+using NTwain.Native;
+using NTwain.Triplets;
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Windows.Forms;
+
+namespace NTwain
+{
+
+  // contains parts for winform/wpf message loop integration
+
+  partial class TwainSession : IMessageFilter
+  {
+    // winform use with Application.AddMessageFilter(<TwainSession instance>)
+    bool System.Windows.Forms.IMessageFilter.PreFilterMessage(ref System.Windows.Forms.Message m)
+    {
+      return CheckIfTwainMessage(m.HWnd, m.Msg, m.WParam, m.LParam);
+    }
+
+    // wpf use
+    IntPtr HwndSourceHook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
+    {
+      handled = CheckIfTwainMessage(hwnd, msg, wParam, lParam);
+      return IntPtr.Zero;
+    }
+
+    private bool CheckIfTwainMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam)
+    {
+      // this handles the message from a typical WndProc message loop and check if it's from the TWAIN source.
+      bool handled = false;
+      if (_state >= Data.STATE.S5)
+      {
+        TW_EVENT evt = default;
+        try
+        {
+          var winMsg = new WIN_MESSAGE
+          {
+            hwnd = hWnd,
+            message = (uint)msg,
+            wParam = wParam,
+            lParam = lParam
+          };
+          // no need to do another lock call when using marshal alloc
+          evt.pEvent = Marshal.AllocHGlobal(Marshal.SizeOf(winMsg));
+          Marshal.StructureToPtr(winMsg, evt.pEvent, false);
+
+          var rc = DGControl.Event.ProcessEvent(ref _appIdentity, ref _currentDS, ref evt);
+          handled = rc == STS.DSEVENT;
+          if (evt.TWMessage != 0 && (handled || rc == STS.NOTDSEVENT))
+          {
+            Debug.WriteLine("Thread {0}: CheckIfTwainMessage at state {1} with MSG={2}.", Thread.CurrentThread.ManagedThreadId, State, (MSG)evt.TWMessage);
+            HandleSourceMsg((MSG)evt.TWMessage);
+          }
+        }
+        finally
+        {
+          // do we need to free it
+          if (evt.pEvent != IntPtr.Zero) Marshal.FreeHGlobal(evt.pEvent);
+        }
+      }
+      return handled;
+    }
+  }
+}
+#endif